Properties of self-compacting rubberized concrete incorporatingrecycled steel fibres reclaimed from scrap tires

The use of the waste obtained from the disposal of end-of-life tires to produce self-compacting concrete (SCC) is considered an effective and sustainable solution to address important environmental problems. This study aims to develop sustainable SCCs by incorporating recycled resources such as crumb rubber and recovered steel fibres from discarded tires. To this, the fresh and hardened properties of the different SCC mixes were assessed. The tests for the fresh properties included the slump flow, L-box, V-funnel, and segregation resistance. In contrast, those for the hardened properties comprised the compressive, splitting tensile, flexural strengths, sorptivity, and ultrasonic pulse velocity. The effect of elevated temperature up to 600 0C on some of the measured properties of the mixtures was also studied. Nine SCC mixtures with a constant water-binder ratio of 0.38 and a total binder content of 450 kg/m3 were designed. The reference mixture with natural sand and the other two mixtures with crumb rubber were considered. Crumb rubber was replaced by natural sand in 10% and 20% volumetric ratios. Each crumb rubber-incorporated concrete mixture contains 0.25%, 0.5%, and 0.75% recycled steel fibres by the total volume for the remaining six mixtures. It was observed that using crumb rubber and recycled steel fibre significantly affected the fresh performance of SCC. Specifically, it led to a reduction in slump flow diameter and L-box values and an increase in Vfunnel time at 5 minutes. Moreover, it was noted that this impact became more pronounced at higher rates. According to the test results, the recycled steel fibres could be used up to 0.5% of the total concrete volume with 10% and 20% crumb rubber-incorporated concretes to meet the EFNARC limits. The results also showed that substituting sand with crumb rubber impacted the hardened properties of SCCs, leading to reduced strength values. Conversely, introducing recycled steel fibres caused a minor increase in compressive strength and considerably improved tensile strength.